I have a three tier setup with a short section of hose going from the mash tun to the boil kettle. At the beginning of the transfer to the boil kettle the wort splashes into the bottom of the kettle. Is this a problem? Should I have a hose that reaches to the bottom of the boil kettle to prevent the splasing?

You are fine. Pre-boil whatever gets into the wort be it microbes or O2 will be snuffed out by the 60-90 minute boil.

I have a single tier system which runs on three march pumps and wort gets splashed from vessel to vessel for 5 hours before the boil. Depending on how quickly I am doing my sparge/run off I sometimes have wort hitting the back of my boil kettle coming in through the ball valve splashing around pretty vigorously without an issue.

Thanks all for the quick responses. I had not suspected it was a problem, but was reviewing a recipe in the IPA section, Bell's Two Hearted Ale Clone, and post #44 by diatonic had his hose running all the way to the bottom. Just checking to see if I was creating a problem by splasing the wort into the BK. I will not worry about it now.

As I understand it, hotside aeration is one of those once-held beliefs that has been mostly debunked by the more experienced brewers here. I don't know the syptoms, but my beers have all been pretty good, so ignorance is bliss, I guess.